I'm lucky here. Gas stations every where. All have 93 at the pump. Plenty of good preminum fuel around here.

That is great! The mistake is that some people throw in higher octane then their engine needs, and that just reduces your horsepower (and costs you more money). Go with the lowest octane you can without detonation.

Mine won't run on 87. Too much comp. too much cam and to much timing to make it run. Older build before quench was the buzz word. Runs great of 93 pings bad on 87. If i kick the timing back to stop the ping it has no balls left. My combo likes 22 degrees initial timing with 38 total.

You have it right then for an old school build! My stock 340 GTS needs premium also, but my hybrid LA/Mag head 360 in my B'cuda runs fine on 87.

When Chrysler designed an engine for street towing with 87 octane fuel, they chose 8.4 static compression for the 1995 8L V10.

When Ford/Toyota designed an economy engine for 87 octane they gave the 2008 Ford Escape I4 a 11.7 to one static compression.

Obviously there is a wide range depending on the camshaft and combustion chamber and other factors.

The attached file is a graph from Japanese research showing how coolant temperature, ignition timing, and static compression ratio affect power and fuel economy:

I'm a fan of building a street motor that you can successfully run on swill. I don't want to be in Wherethehellarewe, NV and find out that 87 octane is the only choice.

I was looking into buying this rotating assembly 1-98111BI - Scat Engine Rotating Assemblies Summit Scat Kit
Not sure if it would run on 87 with Edelbrock 63cc heads and Felpro 1008's, Voodoo 60403 226 int./234 exh.

IIRC, those are 9.0 to 1 compression and big cams that would bleed compression too.

watch the episode of Engine Masters regarding octane is a 10 to 1 Blueprint Motor. very eye opening to say the least.

I have a 416 stroker with Edelbrock heads “63 cc” that we cc’d at 65 +/-1 cc. And 21cc Icon dish pistons with quench pad. Measured at 9.7:1 compression. It less than .035 quench. And has all chamber edges or potential hot spots deburred including chamber matched to bore. I have the older Comp 274-S cam with 236/241 @050 and .502/511”

I can’t run 87 octane. Maybe if I dialed timing way back.

I built a 318/390 stroker using Scat rods, crank, Icon pistons with quench pad. I topped it with EQ magnum heads which cc'd at 64.5. The calculated comp is 9.44, a measured .038 quench, paired with a 218 dur@.050 hyd roller, Edelbrock Pro Flo 4. The engine is in a 68 Coronet Wagon and I run it on 87 octane with 32 total timing. She doesn't like any more than that. I run a 2.76 rear gear and a 904. I built it with mpg and torque a priority. She does no bettter on 93 octane. I'm getting 13 mpg. Not great, but I'm still experimenting with the tune.

Yes. Closed chamber modern head and appropriate cam and it can absolutely be done.
You may even find the engine wants a little less timing than you mentioned.

For what its worth my factory headed 360 with 9-1 comp has been 12.50@110 thru the mufflers on 87. In a 3775lb E body with a 4 speed.
Doug

Care to share your build?

So how come no one is talking about the DCR?

I am trying to work through this question myself (another thread), but it would seem the Dynamic Compression Ratio is really what one needs to be looking at as that accounts for the valve timing events (which are courtesy of your cam).

As such, what I would love to know is the matching OCTANE<=>DCRs people have successfully ran with?

To re-hash that other thread:

previous 360 motor with 10.5:1 static and HE3844 flat tappet:

Not questioning what you say, but it seems something might be off. Less than 10 to 1 with aluminum heads should be no problem with the cam you mentioned. What timing are you running? What is your AFR? Have you tried a colder plug? Also is your block an LA or Magnum?

IIRC 30 adv maybe 28. Can’t remember exactly

Don’t have an AFR meter

Yes tried colder plug

LA block

Don’t forget I live in California with California blend gas: low vapor pressure, no MTBE, etc

IMHO, That blanket statement about aluminum heads dropping compression a full point is overblown


How much measured compression are you running with aluminum heads and 87 octane?

.060" over 360, 9.0-1, Crane hyd roller HR-222/339-2S-12 IG, 1.6 Crane rockers giving .542/.563, LD340 intake w/ divider milled, 650 Holley DP, ported later model 360 heads w/2.02, TTI headers and 2.5" exh. The 12.50s were with slicks and a 4.30 gear. It's been 12.70@107 w/ 3.55 and old BFG drag radials. Always run with the air cleaner and exhaust. It has the factory 2.47 1st 4 speed and a Centerforce dual friction clutch.
Doug

Thanks for sharing. Also surprised this thread has this much action being as it was brought back from the dead 10/03/09 last post